As a business evolves through its start up, growth, maturity and decline
phases it is evident that the business marketing plan and business marketing
strategies must change.

A great place to start finding information on business marketing strategy is
to look at any academic marketing books. They discuss cycle stages
and adjustments. Further, they have case studies used for exercises thus
don't provide what the company did but can be of help. Also there are case
examples that do discuss what a company did.

Have a look at business/marketing journals (the dinosaur types: print) and
check out Harvard Business Review (print) and also the Harvard Business
School Press online. Keyword searching can do wonders!

Pretty easy to find examples of what you seek. Just about every issue of
Business Week, Forbes, Fortune contains stories on startup, growth, mature,
decline. Just have to dig through the stacks, in some cases the virtual
stacks.